1. Field of the Invention
The invention relates to weaving machine heald frame fitted with an upper and a lower cross-sectionally contoured rail, hereafter rail, for holding the healds which are held by guide elements located at the ends of the healds to the rails.
2. Related Art
Several heald frames of this kind constitute a so-called heald frame system. The individual heald frames of this system are alternatingly raised and lowered by a heald frame machine in order to form sheds using heald-guided warps between which fillings may be inserted. The rails and the heald guide elements typically have geometries such that, in one direction of heald frame motion, one of the rails rests by a drive surface against a cooperating surface of the heald guide elements to thereby drive such healds. In the other direction of motion, a drive surface of the other rail will drive a cooperating surface of the heald guide elements which are associated with it. Because the heald frames and the healds expand on account of heat and forces applied by the warps, and because manufacturing tolerances have to be provided for both, and because additionally the healds must be displaceable along the rails, for instance to insert or repair warps, a play of about 2-3 mm is provided for the healds between the drive surfaces of the rails and the cooperating surfaces of the guide elements. When the frames move up and down, the healds will move by said 2-3 mm relative to the rails. These motions result in impacts causing on one hand noise and on the other hand heald vibrations. At high weaving rates, these motions and particularly the thereby caused vibrations may break the healds and/or the heald frames and/or the warps.
To avoid such problems, it is known from WO 97/23396 to reduce the play between the healds and the rails by providing one or more shims fitted onto one of the rails to reduce the gap between these heald drive surfaces of this rail and the cooperating surfaces of the heald guide elements down to a slight play of about 1 mm. These shims are made of plastic, and consequently damping is attained as well. In this manner noise and the risk of damage may be reduced, although some drawbacks may be incurred regarding operability. Because the heald play is reduced longitudinally, the longitudinal movability of the healds and their movability in the direction of the rails also is restricted. As a result, an operator repairing a yarn break may be somewhat hampered and it is even possible that the healds could be bent in the course of making repairs.
The objective of the present invention is the reduction of noise and furthermore the reduction of potential damage caused by heald vibration.
This problem is solved in that a damping stop made of material with damping properties is provided adjacent at least one end of the healds and in that the gap between this stop and the adjacent end of the healds shall be smaller than the gap between the guide element ends and the rail surfaces opposite the stop.
In this design the healds shall be driven at least in one direction by the damping stop or they shall impact the stop in one direction, as a result of which noise will be significantly reduced. Also, at least when the healds are driven in one direction or when impacted in one direction, damping shall take place and heald vibrations will be substantially reduced. This reduction in noise and adverse effect of vibrations also shall be the case for plays of larger magnitudes, for instance of 2-3 mm or more, and consequently there would be no restriction on the relative movability of the healds in the longitudinal rail direction or in their own longitudinal direction. Means are thus provided to the skilled designer to reduce the danger of noise and creaking movability or shiftability by controlling the play or to trade off somewhat more noise and somewhat greater danger of vibrations against improved heald movability.
Preferably stops shall be fitted at both heald ends. In this manner driving of the healds and the impact of the healds on drive elements takes place solely against the damping stops. The rails in accordance with this design merely provide lateral guidance. Consequently the longitudinal heald play may be selected almost arbitrarily, that is, it may be comparatively small and entail less movability and longitudinal excursion, or it may be comparatively large with commensurately good movability and longitudinal excursion.